It is known, in the industrial and agricultural fields, the use of apparatus and methods for treating wastewater and sludge comprising sewage in order to dispose of the undesired substances, in order to reduce the toxicity and purify such water and/or sludge in order to enable a correct recovery or disposal.
Particularly, methods and apparatus for treating residential and/or industrial wastewater using chemical, mechanical and/or thermal processes configured to treat the substance in order to reduce at a minimum the presence of micropollutants, are known. Since the toxicity of the wastewater and/or sewage is at least partially caused by the presence of pollutants, such as ammonia nitrogen NH3 and carbon dioxide methods/apparatus for treating sewage, capable of extracting from the latter ammonia dissolved as NH4+ and ensuring the abatement of the ammonia nitrogen NH3 have been introduced.
For example, a first approach described in patent application WO2010/0015928 A1 provides a process of extracting ammonia nitrogen (NH3) from wastewater. The process provides the introduction of the wastewater in a reactor inside which basifying agents adapted to react with the wastewater for taking the pH to the natural value are supplied: so that, ammonia nitrogen contained in the wastewater tends to separate from the latter as a gas (NH3). The process provides the generation of a gaseous flow inside the reactor, adapted to extract ammonia nitrogen developed during the chemical reaction between wastewater and basifying agents. In order to increase the ammonia nitrogen extraction efficiency, the process provides a step of heating the wastewater and a treating step by means of ultrasound.
Despite the method described in first solution enables to extract ammonia nitrogen from wastewater, the method itself is not devoid of disadvantages and limitations.
De facto, the wastewater treatment by means of chemical additives make the method expensive and difficult to control. Specifically, the treatment by means of chemical additives is hardly manageable under conditions wherein it is necessary to treat wastewater having different concentrations of dissolved substances: in this case, the adjustment of the additive to be introduced in the substance is hardly calculatable and adaptable to diversified conditions of the liquid. It should not be disregarded that the chemical treatment of wastewater substantially prevents from reusing the liquid itself, for example for producing compost or biogas.
In a second approach described in documents U.S. Pat. No. 6,555,011 and DE102004050493, it is provided a treatment for sanitizing and purifying biological fluids. The method provides a first step wherein the fluid passes through a reactor defining inside a forced passage for the fluid. Inside the reactor and at the forced passage points there are devices adapted to sanitize the fluid. Particularly, the method provides the formation of predetermined areas with high energy density at the forced fluid passages: in this way, when the fluid flows through the reactor, the devices are capable of energising the latter in order to purify and sanitize it.
In a third approach described in document WO 2007/115660 it is provided a method for treating sewage in order to produce a fertilizer; the object of this method consists of removing dissolved substances, particularly ammonia nitrogen NH3 and carbon dioxide CO2, present in the liquid to be treated.
More particularly, the method provides the extraction of the ammonia nitrogen from sewage thanks to the use of ultrasounds, and the depuration of the stripping gases by a solution of water and sulphuric acid.
Still more particularly, the method comprises a first step of introducing sewage in a first tank; the sewage is treated by ultrasounds at a frequency comprised between 0.2 MHz and 1.7 MHz. The use of ultrasounds at the specific frequency generates inside the fluid a phenomenon called cavitation which enables to degas the fluid and release CO2 and NH3 from the same. Gases (CO2 and NH3) released by fluid, are then introduced, by means of a compressor, in a second tank. Inside the second tank there is a solution containing sulphuric acid (H2SO4) which is made soluble with the gases (CO2 and NH3) extracted from first tank. Also the solution present in second tank is treated by ultrasounds at a frequency of 1.7 MHz, which, in this step, enable to release ammonium sulphate ([NH4]2SO4) and carbon dioxide.
Also the methods/apparatus described in second and third approaches are not devoid of disadvantages and limitations. Particularly, these methods are not capable of ensuring an acceptable abatement of bacteria present in the liquid adapted to ensure a reuse of the latter for forming a fertilizer.